Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
  • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
  • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
  • C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2375/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
  • C08J2375/04—Polyurethanes

Definitions

• the present invention relates to a process for the preparation of flexible polyurethane foams, wherein liquid carbon dioxide is used as blowing agent.
• EP-A-0,645,226 and WO-A-98/30376 are produced by bringing together under pressure the reactive foam components including the liquid carbon dioxide and subsequently passing the resulting foaming mixture through a pressure reducing device after which the polyurethane foam is formed.
• Bringing together the foam components may involve premixing liquid carbon dioxide under pressure with at least one of the other foam components and then mixing the component containing the liquid carbon dioxide with the other reactive foam components under pressure (e.g. WO-A-96/00644 and EP-A-0,645,226). It may also involve bringing together all foam components without premixing and directly passing them through a pressure reducing device (e.g. WO-A-98/30376) .
• the foam components typically include a polyol component, a polyisocyanate component, one or more catalysts, a surfactant and a blowing agent.
• pressure is applied to keep the carbon dioxide in the liquid state, i.e. normally the liquid carbon dioxide is dissolved in the other foam components and the pressure applied ensures that no gaseous carbon dioxide is present.
• the foaming mixture is discharged thereby releasing the pressure so that the liquid carbon dioxide will become gaseous and will expand the foam formed.
• the different processes mainly differ in the way in which one or more of the components is mixed with the liquid carbon dioxide and/or the way in which the foaming mixture is discharged .
• a process for continuously producing low density polyurethane foams wherein liquid carbon dioxide is mixed under pressure with the other foam components and subsequently the resulting foaming mixture is discharged through a permeable discharge head to form a froth.
• the discharge head comprises at least one diffuser element having a structure which causes division, divergence and convergence of flow paths within the axial thickness of the diffuser element, all relative to the direction of the flow of components through said diffuser element.
• the foam components including the liquid carbon dioxide are brought together under pressure and are passed through a permeable discharge head where the pressure is reduced.
• the discharge head comprises a diffuser element consisting of several individual woven wire meshes sintered together to form a composite element. The structure of the diffuser element enables division, divergence and convergence of flow paths in three dimensions in the direction of the flow therethrough.
• foams are produced using carbon dioxide as blowing agent, wherein at least one of the foaming components is mixed with carbon dioxide under pressure to produce a mixture containing carbon dioxide in liquid form, subsequently mixing this mixture with the other reactive foam component to form a foamable reactive mixture and then expanding this reactive mixture by subdividing it into a large number of individual flows at high shear rates. Suitably this is attained by passing the reactive mixture through at least one fine-meshed screen. Finally, the foam product is cured.
• the present invention particularly aimed at improving the hardness of the foams produced and at improving the mechanical strength and load bearing properties. Furthermore, the present invention aimed at finding a method for producing polyurethane foams having improved processability, e.g. in terms of cell-opening, while using liquid carbon dioxide as blowing agent.
• the present invention relates to a process for the preparation of flexible polyurethane foams comprising the steps of
• step (b) releasing the pressure and allowing the mixture obtained in step (a) to react into a flexible polyurethane foam
• the polyol component comprises a polymer polyol consisting of at least one polyether polyol having an average nominal functionality of at least 2.5 with dispersed therein from 2 to 50 wt% based on total weight of polymer polyol of polymer particles, whereby the particle size of essentially none of these polymer particles exceeds 50 micron.
• such polyether polyol is obtained by reacting one or more alkylene oxides like ethylene oxide and propylene oxide with a suitable initiator compound containing three or more active hydrogens which can react with the alkylene oxide.
• the base polyol is a polyether polyol having a molecular weight in the range of from 250 to 12,000, preferably from 500 to 6,500, more preferably from 2,500 to 6,000; an average nominal functionality (Fn) of at least 2.5, more preferably from 2.5 to 6.0 and most preferably from 2.5 to 4.0; and an ethylene oxide content of from 0 to 50 wt%, preferably 0 to 20 wt%, based on total weight of polyether polyol.
• the polymer dispersed in the base polyol may in principle be any such polymer known to be applicable for this purpose.
• suitable polymers include the polymers based on ethylenically unsaturated monomers and particularly polymers of vinyl aromatic hydrocarbons, like styrene, alpha-methyl styrene, methyl styrene and various other alkyl-substituted styrenes . Of these, the use of styrene is preferred.
• the vinyl aromatic monomer may be used alone or in combination with other ethylenically unsaturated monomers, such as acrylonitrile, methacrylonitrile, vinylidene chloride, various acrylates and conjugated dienes like 1, 3-butadiene and isoprene.
• Preferred polymers are polystyrene and styrene-acrylonitrile (SAN) copolymers .
• Another suitable class of polymers are the polyurea and polyurethane polymers. Particularly the condensation products of polyhydric alcohol amines and aromatic diisocyanates are very useful in this respect.
• a very much preferred polymer is the condensation product of triethanol amine and toluene diisocyanate (TDI) .
• the dispersed polymer is preferably present in an amount of from 5 to 40% by weight based on total weight of polymer polyol.
• preferred amounts are between 10 and 35% by weight, whilst in case of polyurea polymers and condensation products of polyhydric alcohol amines and aromatic diisocyanates the preferred amount of polymer is between 5 and 20% by weight.
• the polymer particles dispersed in the polyol should have a particle size of not more than 50 micron, i.e. essentially none of the polymer particles should have a particle size above 50 micron.
• the polymer polyol is suitably filtered before use in the process according to the present invention. Any filtration technique known in the art for filtering suspensions of small .particles in a liquid medium can be used. Yet another possibility of obtaining polymer polyols which are essentially free of polymer particles having a particle size above 50 micron is by using a method for preparing polymer polyols, wherein very small polymer particles are formed with a very narrow particle size distribution. Such a method is, for instance, disclosed in EP-A-0, 786, 480. The invention will now be illustrated by the following examples without limiting the scope of the present invention to these particular embodiments.
• Example 1 Example 1
• a prefiltered polymer polyol was tested on an experimental slabstock foam unit equipped with a device for introducing liquid carbon dioxide into a foam formulation (a Novaflex liquid CO2 device ex Hennecke; Novaflex is a trademark) .
• the prefiltered polymer polyol contained 10.5 wt% polystyrene particles dispersed in a polyether polyol having an OH-value of 46 mg KOH/g, a molecular weight of 3500, an ethylene oxide content of 11 wt% and a nominal average functionality of 3.0, and contained less than 5 ppm filter retentate when passed over a 41 ⁇ m filter in a standard filtration.
• Hardness 40 % 2.9 kPa (DIN 53577)
• Tensile strength 92 kPa and Elongation : 110 % (ASTM 3574) .
• Example 2 On a commercial slabstock foam unit equipped with a similar liquid CO2 device, the same formulation as used in Example 1 was tested containing the same 10.5 wt% polymer polyol as used in Example 1, except that this time the non-filtered form of the polymer polyol was used. In a standard filtration on a 41 ⁇ m filter 23 ppm retentate was found for this polymer polyol. When processing the formulation over the slabstock foam unit, rapid pressure build up was observed and a large number of particles was found in the discharge part of the liquid CO2 device, as a result of which the device was blocked. Comparative Example 2
• Example 2 On the same unit as in Example 1, the same formulation as in Example 1 was tested, except that it contained a polyether polyol in stead of a polymer polyol. Thus, no polymer particles were present.
• the polyether polyol used was the same polyol which was used as the base polyol in the polymer polyol of Example 1 (i.e. having an OH-value of 46 mg KOH/g, a molecular weight of 3500, an ethylene oxide content of 11 wt% and a nominal average functionality of 3.0).
• OH-value 46 mg KOH/g
• a molecular weight of 3500 i.e. having an OH-value of 46 mg KOH/g, a molecular weight of 3500, an ethylene oxide content of 11 wt% and a nominal average functionality of 3.0.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polyurethanes Or Polyureas (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

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• 1999
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• 2000
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• 2001
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